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Lennox 3ton Rooftop question.

Lennox RTU
M#LCH036H4EN Y
S#5611H05061

Copland Scroll 2 Stage
M#ZPS30k4E-TF5-130
S#11AG38D4N
410A

Unit is new and was just set a few months ago. Checked Prodigy control and find 2 Low pressure switch faults, and the third had locked it out. Reset system, and checked operation. System runs perfectly in 1st stage cooling. Pressures are great, Comp, fan and blower amps all within range and at proper speed. Everything is running according to design.

This is a single circuit system. Every component is used in 1st stage as 2nd stage. Only component that changes is the compressor. I am thinking the bypass ports are not closing and the compressor remains at 67% capacity. With the increased blower speed suction is falling off. I have never seen this before, so any input you guys have is appreciated.

One thing i did not do was remove charge, and recharge to factory specs. I recommended that we rule that out before we condemn anything. I see no signs of oil anywhere, and I checked pressures according to unit chart and everything is up too par. I truly don't believe this is a charge issue.

Very simple. Drops straight into a room, and return pulls from the room. No duct issues at all.

No EEV, but just a normal TXV which i have diagnosed as operating properly. Again, this is a single circuit with the new ultratech Technology. First i have ever seen, but all i can come up with as a possible cause. I have checked this thing inside and out! Including all sensors on prodigy controller. SAT sensor seems to be a little out of wack to my readings, but that is the least of my problems at the moment. I have not totally ruled out a charge issue yet. I didn't have the equipment on site to remove charge, and recharge to factory specs. I did put unit into high mode, and check subcooling, and chart for units discharge pressure and all corresponded to what i was seeing. Guys this one is just off the wall for me. I won't sleep till i get to go back and figure this one out! LOL

Very simple. Drops straight into a room, and return pulls from the room. No duct issues at all.

No EEV, but just a normal TXV which i have diagnosed as operating properly. Again, this is a single circuit with the new ultratech Technology. First i have ever seen, but all i can come up with as a possible cause. I have checked this thing inside and out! Including all sensors on prodigy controller. SAT sensor seems to be a little out of wack to my readings, but that is the least of my problems at the moment. I have not totally ruled out a charge issue yet. I didn't have the equipment on site to remove charge, and recharge to factory specs. I did put unit into high mode, and check subcooling, and chart for units discharge pressure and all corresponded to what i was seeing. Guys this one is just off the wall for me. I won't sleep till i get to go back and figure this one out! LOL

Just wondering, are you sure the expansion valve is okay?

A new power element sometimes works wonders.

Perhaps the sensing bulb was overheated, or maybe lost a portion of its charge.

Your compressor current is increasing on high capacity, so it would seem the load / unload function is working.

This is an ECM direct drive blower motor?

Have you verified all of the correct settings in the Prodigy controller?

The temp conditions posted look pretty mild..

Your suction pressure drops off and the SH goes way up on high stage..

It appears the valve is not feeding enough refrigerant for full capacity.

Maybe pop a new power element on there and see what happens.

Or a small shot of refrigerant?

Yes direct drive.
Yes, all setting verified in controller.
Yes, SH/SC normal on first stage. SH high, and SC normal on 2nd stage.
Whats this power element you speak of? Please explain?
Yes, I am going to weigh in a charge next time i am there. I would love if that worked, but just don't think that is it.